Suboptimal Light Conditions Influence Source-Sink Metabolism during Flowering

Area of Science:

• Plant Physiology
• Horticultural Science
• Molecular Biology

Background:

• Flower forcing in azaleas (Rhododendron simsii hybrids) requires significant carbohydrate resources.
• Understanding carbohydrate metabolism is crucial for optimizing flowering quality and yield.

Purpose of the Study:

• To investigate carbohydrate utilization during flower forcing in azaleas under varying light conditions.
• To assess the role of sucrose synthase gene expression (RsSUS) in carbohydrate partitioning.

Main Methods:

• Monitoring carbohydrate levels (glucose, fructose, sucrose), invertase activity, and RsSUS gene expression in leaves and petals.
• Comparing flower forcing under suboptimal (natural) and optimal (supplemental light) conditions after cold treatment.
• Assessing post-production flowering quality and sucrose metabolism.

Main Results:

• Petals showed increased glucose, fructose, and invertase activity, with decreased sucrose during flowering.
• Suboptimal light increased RsSUS expression in leaves, indicating high carbohydrate demand, but leaf carbohydrate levels were lower.
• Plants under suboptimal light exhibited poor flowering, relying on stored carbon from optimal light conditions.

Conclusions:

• Azalea flower opening is dependent on carbohydrate import from leaves.
• Carbohydrate supply from leaves is a limiting factor for flowering under suboptimal light conditions.
• Optimizing light conditions is essential for accumulating sufficient carbohydrates to support robust flower development.